'How Do You Know' it's not a sitcom?

When it comes to sharp and snappy dialogue between two people in a struggling relationship, James L. Brooks is the master.

He was the “As Good As It Gets” writer who gave Jack Nicholson his classic confession of love to Helen Hunt with “You make me want to be a better man.”

In his new comedy about struggling relationships, “How Do You Know,” Brooks gives a similar line to Owen Wilson's shallow ballplayer Matty, trying to make up to Reese Witherspoon's miffed Lisa Jorgenson.

“I don't know that I can do great,” Matty says with his puppy dog eyes, “but I know I can do better!”

That's it? That's the line?

Yep, I know. It's not on the same level as the “better man” line, but then, “How Do You Know” is an insightful and amusing rom-com that isn't quite on the same level as either “As Good As It Gets” or Brooks' 1987 classic “Broadcast News.”

Here, the characters are a little broader, a little less nuanced and a whole lot more sitcomy in their words and deeds.

Witherspoon's Lisa, 27, has just been bounced from her professional ball team and is in personal free fall.

Across the city, George (Paul Rudd), an executive for a company owned and commanded by his father Charles (Nicholson), gets bad news.

The feds are investigating him and his company for fraud on charges of misstating earnings reports.

Lisa hooks up with Matty, Wilson's womanizing baseball pitcher who keeps entire wardrobes and cosmetic cases stocked for the convenience of his overnight conquests.

Is Lisa's self-esteem so low that she thinks it's a good idea to take up with this guy?

Matty? The same guy whose fellow ballplayers coach him on true love with this observation: “I figure I'm in love when I wear a condom with the other girls!”

Lisa agrees to have lunch with George, who falls to pieces. Normally, this would be death for a first impression.

But Lisa responds with understanding and kindness.

Besides, in Brooks' Hollywood rom-com world, we suspect it's just a matter of time before Lisa regains her senses, drops the well-meaning but totally insensitive jock and picks up with the grand-jury-indicted whiny boy.

Here Brooks brings his A-game to the dialogue in several breezy, self-revealing exchanges.

But everyone in “How Do You Know” appears to be cranking their characters up to oddly manic levels.

Witherspoon resorts to borderline mugging as she emotes Lisa's moods of the moment.

Rudd, usually a paragon of comic restraint, creates a character a little too needy for our approval to be adorable. (Not that he doesn't have his adorable moments.)

Nicholson's CEO is all flustered arm flagellations and huffing, puffing line deliveries, as if compensating for an underdeveloped character.

Only Wilson's kind-spirited dimwit bats 500 in this rom-com, a thin but entertaining tale of scar-crossed lovers who could easily have been created by Neil Simon.

“How Do You Know”

★★★

Starring: Reese Witherspoon, Paul Rudd, Owen Wilson, Jack Nicholson

Directed by: James L. Brooks

Other: A Columbia Pictures release. Rated PG-13 for language, sexual situations. 116 minutes